Beneficiation of a Greek serpentinic nickeliferous ore Part I. Mineral processing Stella Agatzini-Leonardou * , Ioannis G. Zafiratos, Dionysios Spathis Laboratory of Metallurgy, Department of Mining and Metallurgical Engineering, National Technical University of Athens, 9, Ir. Polytechniou Street, Athens 15780 Zografos, Greece Received 18 February 2004; received in revised form 24 May 2004; accepted 28 May 2004 Abstract Serpentinic ore, from the ‘‘Kastoria’’ nickeliferous deposit in Northern Greece, was first processed to reject as much of its calcite content as possible. Partial separation of calcite from the ore was achieved by the use of a strong magnetic field, the extent of which depended on feed particle size. The losses of nickel in the nonmagnetic product were about 5%, while the percentage CaO removal was about 37%. Based on the experimental findings, a mineral processing scheme was devised and applied in order to prepare a suitable sulphuric acid heap or agitation leaching feed. D 2004 Elsevier B.V. All rights reserved. Keywords: Nickel laterite ores; Serpentine; Magnetic separation; Autogenous grinding; Calcite removal 1. Introduction Greece is the only EU country with extensive but low-grade nickel laterites. They mainly occur as limonitic laterites and, to a lesser extent, as serpentinic laterites. The Greek laterites are unique in the world in that they are sedimentary and have originated by transport and sedimentation of laterite-derived mate- rial, generated by weathering of ultramafic rocks (Kuhnel et al., 1974; Golightly, 1979; Manceau and Calas, 1986; Skarpelis et al., 1993; Orphanoudaki et al., 1997; Boskos et al., 2000). The Greek limonitic laterites have been exploited to produce ferronickel via a pyrometallurgical route. This involves prereduction of the ore in rotary kilns, reduction smelting in electric furnaces, and upgrading of the raw ferronickel in a converter to the final 20– 25% Ni grade. Because of the rising cost of energy, the method is economically marginal when ore with 0.95–1% nickel is treated and is uneconomic for lower grade laterites. Direct application of the above pyrometallurgical method to existing serpentinic lat- erites is not feasible because the slag produced is difficult to melt, resulting in higher energy require- ments and poor phases (metal – slag) separation. An innovative integrated hydrometallurgical meth- od for nickel and cobalt extraction from Greek limo- nitic laterites has been developed and patented (Agatzini-Leonardou and Dimaki, 1994; Agatzini- Leonardou and Dimaki, 2001; Agatzini-Leonardou and Karidakis, 2000; Agatzini-Leonardou et al., 2000) as a result of many years of work at the 0304-386X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2004.05.005 * Corresponding author. Tel.: +30-210-7722234; fax: +30-210- 7722218. E-mail address: agatzi@metal.ntua.gr (S. Agatzini-Leonardou). www.elsevier.com/locate/hydromet Hydrometallurgy 74 (2004) 259 – 265